1. Field of the Invention
This invention relates to a semiconductor integrated circuit device for preventing a signal interference between wirings.
2. Description of the Related Art
Recently, it has been strongly required to enhance the integration density of semiconductor integrated circuit devices, and the integration density has increased by further developing the element miniaturizing technique and multi-layered wiring technique. With the development of the element miniaturizing technique, the line width of the wiring and the distance between the wirings tend to be reduced. As the distance between the wirings becomes smaller, a signal interference between the wirings which can be neglected in the prior art becomes significant, thus making it difficult to effect the precise signal transmission.
FIG. 1 is a cross sectional view showing the schematic construction of the conventional semiconductor integrated circuit device. As shown in FIG. 1, wiring 81 formed of a first-layered conductive layer and wiring 82 formed of a second-layered conductive layer are disposed in insulation layer 80. Parasitic capacitances C0, C1 and C2 are present between wirings 81 and 82. Capacitance C0 represents an equivalent parasitic capacitance existing along a straight line passing those portions of wirings 81 and 82 which face each other, and capacitances C1 and C2 each represent an equivalent parasitic capacitance existing along an outwardly curved line passing side portions of wirings 81 and 82. Generally, capacitances C0, C1 and C2 have the relation of C0&gt;&gt;C1, C2. Assume now that different signals or voltages are transmitted along wirings 81 and 82. For example, an analog signal shown in the waveform diagram of FIG. 2(a) is transmitted along wiring 81 and a digital signal shown in FIG. 2(b) is transmitted along wiring 82. When the signals are transmitted along wirings 81 and 82, interference signals occur because of the presence of parasitic capacitances C0, C1 and C2. As a result, the analog signal is influenced by the digital signal and a distortion component is introduced into the analog signal as shown in FIG. 2(c). Therefore, it becomes impossible to correctly transmit the analog signal. Further, the semiconductor integrated circuit device having a miniaturized structure and a multi-layered wiring structure tends to be influenced by the peripheral wirings and subject to the signal interference caused therebetween, thus making it difficult to correctly transmit the signal.